The present invention relates to gaskets for use in providing a liquid-tight seal between an opening in a sidewalk and a pipe and more particularly to a gasket for providing an excellent liquid-tight seal with a corrugated pipe and which is easy to install and use.
Gaskets have been typically utilized for providing a liquid-tight seal between a sidewalk opening, for example, an opening provided in a cast member employed in septic, storm water or waste water systems, and a pipe extending into the opening.
Such gaskets are typically resilient, annular-shaped, rubber or rubber-like members having an embedment portion which is embedded in the sidewalk opening of a cast member when the member having the sidewalk opening is cast, and a pipe engaging portion for surrounding and engaging the outer periphery of the pipe. Alternatively the gasket may be placed in an opening which is cored or otherwise formed in a cast member, the gasket having a portion extending into the formed opening and held therein by means of an expansion type clamping band. This type of mounting of a gasket in an opening in a cast member is referred to as being xe2x80x9cjacked-inxe2x80x9d an opening.
A liquid-tight seal is provided by causing the pipe engaging portion of the gasket to undergo stretching when the pipe is pushed through the gasket or, alternatively, the liquid-tight seal is obtained by placing a clamping band about the pipe engaging portion so as not to rely exclusively upon the stretched gasket absent a clamping band for a liquid-tight seal.
All gaskets presently available provide an adequate liquid-tight seal with cylindrical pipe having a smooth outer periphery. However, pipe having an undulating periphery presents unique problems making it difficult to obtain an adequate liquid-tight seal employing presently available gaskets.
Pipe having a smooth, cylindrical-shaped outer periphery, and typically cast from concrete, are rapidly being replaced for use in underground sewage systems and the like by plastic pipe, which provides more than adequate structural strength while significantly reducing the cost and weight of such pipe as compared with concrete pipe, thereby significantly reducing fabrication, handling, transportation and installation costs.
To obtain plastic pipe of the desired structural strength, some plastic pipe is formed to have a corrugated outer-peripheral shape defined by alternating, annular shaped recesses and projections each recess and projection having a substantially U-shaped cross-section. The interior of the pipe is provided with a smooth, cylindrical-shaped inner periphery integrally joined to the base of each annular recess, which pipe structure yields a pipe of light weight and get significantly large structural strength.
Corrugated pipe of the type described here in above, due to their method off fabrication, are often provided with vent tubes which project radially outward and into each annular recess, said projections lying along an imaginary line parallel to a longitudinal central axis of the pipe at xe2x80x9c12 o""clock and xe2x80x9c6 o""clockxe2x80x9d and extending in an outward radial direction from the cylindrical interior portion.
In order to provide a water-tight seal, the pipe engaging portion of the gasket encircles and engages the outer periphery of the corrugated pipe. Due to the configuration of the corrugated pipe, it is impractical, if not impossible, to obtain a water-tight seal employing only a resilient gasket, i.e., employing a gasket absent a clamping band.
One technique for providing a water-tight seal is to mount a pipe adapter upon the corrugated pipe by stretching the pipe adapter until it is positioned in the proper location, encircling one of the annular projections. The end of the gasket to be water-tightly sealed to the pipe is then pulled over the adapter. A clamping band is placed over the gasket and then tightened. Placement of the take down clamp is critical, if it is not placed properly, failure can occur, in particular if the clamp straddles the pipe and adapter, unequal compression can be the result.
This design has the disadvantage of providing rubber to rubber contact between the adapter and the gasket causing undesirable kinking when the clamping band is tightened which ultimately results in the failure to provide a water-tight seal. In addition, the installation is both tedious and complicated, due to the necessity of significant exertion for stretching the adapter or, to state it in another way, it is tedious and difficult to mount the adapter and push the corrugated pipe through the gasket.
It is therefore desirable to provide a gasket and clamping assembly which is easy to apply, especially one capable of insertion of the corrugated pipe into the gasket without undue exertion yet one which provides an excellent liquid-tight seal between the corrugated pipe and the gasket.
The present invention is characterized by comprising, in one embodiment thereof, a gasket having an inner diameter which is greater than the outer diameter of the corrugated pipe to facilitate easy insertion of the corrugated pipe into the gasket without any exertion whatsoever.
The gasket, in one embodiment, is provided with an which is embedment portion embedded into the cast member during the casting operation and having an annular pipe engaging portion connected to the embedment portion by an annular curved or xe2x80x9cradiusxe2x80x9d portion. The gasket, in another embodiment, is modified so that the portion inserted into periphery of and engaging at a previously formed opening in a cast member has no embedment portion, and in place thereof, is provided with a substantially cylindrical-shaped outer surface for engaging the opening and an inner periphery provided with an annular recess for receiving and aligning an expansion-type clamping band which is expanded in circumference to press the opening engaging portion into firm, liquid-tight engagement with the opening into the cast member. The gasket is placed under compression between the expansion type clamping band and the opening in the cast member sufficient to retain the liquid-tight seal.
The pipe engaging portion is provided with a pair of integral projections about the outer periphery thereof, defining a recess for receiving and aligning a clamping band.
In one embodiment, the recess receiving the clamping band is positioned about an annual recess in the corrugated pipe. The clamping band, when tightened, has a width which is selected to cause the pipe engaging portion of the gasket to form an excellent liquid-tight seal with opposite sides of the annular recess while at the same time being prevented from reaching and engaging the base of the annular recess to prevent engagement of the gasket with a possible vent tube projection formed in the corrugated pipe during fabrication thereof.
In one preferred embodiment, the outer periphery of the pipe engaging portion is provided with integral, spaced parallel projections which define an annular recess for receiving and positioning an adjustable clamping band. The clamping band has a width relative to an annular recess within the corrugated pipe designed to urge the pipe engaging portion into the annular recess and to form a liquid-tight seal between opposite annular sides of the clamping band and the pipe engaging portion which is urged against opposite tapering sides of the annular recess. The adjustable clamping band is tightened sufficiently to assure a liquid-tight seal while preventing the gasket from engaging the base of the annular recess to prevent the portion of the gasket within the annular recess from forming an irregular shape and kinking which would otherwise diminish the assurance of a liquid-tight seal.
The pipe engaging portion which is urged into the annular recess cooperates with the annular recess to form an annular pocket which acts to further enhance the liquid-tight seal as a result of the air compressed within this annular pocket.
The clamping band may assume any one of a variety of different designs including one in which the clamping band is of the type having a threaded member which cooperates with recesses of the clamping band to tighten the clamping band when the threaded member is rotated in a given direction. As another alternative design, the clamping band may be of the type having one or more clamping levers which, when rotated from the open to the closed position, draws the clamping band more tightly about the gasket.
The gasket and clamping band are designed to accommodate corrugated pipe over a wide of range inner diameters.
In one embodiment, the clamping band may be fitted within an annular-shaped saddle having a recess about its outer periphery for receiving the clamping band. The opposite annular sides of the saddle which have a width greater than the width of the clamping band are designed to adapt the gasket for use with corrugated pipe of larger diameters without changing the width of the clamping band. Alternatively, both the clamping band and the saddle may be of increasing width to accommodate corrugated pipe of increasing inner diameter.
The clamping band may also be placed within a recess of the pipe engaging portion which is aligned with an annular peak of the corrugated pipe. In this embodiment, the clamping band may be provided with an inner periphery of a concave shape which generally conforms to the shape of the annular peak. The clamping band is tightened sufficiently to provide a liquid-tight seal.
Two clamping bands may be provided in still another embodiment and both of the clamping bands urge spaced portions of the pipe engaging portion into spaced apart annular recesses. Alternatively, one of the clamping bands may urge one portion of the pipe engaging portion against an annular peak while the other clamping band urges another portion of the pipe engaging portion into an annular recess spaced therefrom.
The gasket is preferably extruded so as to have a cross-section which is substantially the same as the cross-section assumed by the gasket when in the position in which the embedment portion is embedded within the cast member and the pipe engaging portion is clamped to a corrugated pipe. A gasket of this type which is installed into a pre-formed opening, is extruded in a similar fashion but with the embedment portion being eliminated and replaced by a substantially cylindrical-shaped outer surface and an annular recess provided in its inner periphery for receiving an expansion type clamping band.
During casting employing a gasket having an embedment portion, the pipe engaging portion of the gasket inserted into the embedment portion is pulled out so as to substantially define an elongated cylinder together with the embedment portion, the gasket being maintained in this position by mounting upon a one-piece, hole former mandrel.
The hole former mandrel is placed between inner and outer mold members. The casting material is then placed within the mold assembly causing the embedment portion to be embedded within the cast material. The radius portion is in the shape of an annular xe2x80x9chumpxe2x80x9d when placed upon the hole former. In the case of the gasket inserted into a performed opening in a cast member, the gasket is not placed in the mold assembly but is installed in a performed or xe2x80x9ccoredxe2x80x9d opening.
After the cast member having a gasket embedded therein is stripped from the mold assembly, the gasket is pulled through the embedment portion to assume the pipe connection position. The xe2x80x9chumpedxe2x80x9d radius portion, which provides the gasket with a xe2x80x9cmemory,xe2x80x9d causes the gasket to snap into the final use position (which is the same position as when the gasket is extruded) due to the memory of the gasket.
The gaskets of the present invention, may be produced either through the use of a molding or an extruding operation. A gasket, in one preferred embodiment, has a generally annular shape comprised of an outer embedment portion and an inner pipe engaging portion and an intermediate radius portion of substantially U-shaped cross-section joining the embedment and pipe engaging portions, the inner (pipe engaging) portion being rolled outward or rotated into the outer (embedment) portion so that its free end extends beyond the free end of the outer portion before being placed on a hole former mandrel preparatory to a casting operation. This orientation of the gasket is the same orientation as the orientation of the gasket when extruded, for example.
The outer, embedment portion has a radially outwardly extending projection adapted to be embedded within the cast material and having a cross-section which enhances the anchoring of the embedment portion within the cast member.
The pipe engaging portion has a recess on its outer periphery for receiving and positioning a clamping band.
During casting, the inner portion is pulled out of the embedment portion through the use of a hole former, for example, so as to generally define an extended annular portion extending beyond and away from the outer embedment portion. This state is retained by pulling the gasket over the hole forming mandrel.
The hole forming mandrel is mounted in any conventional manner between a jacket and a core of a molding assembly. Although the inner and outer portions of the gasket retain a substantially cylindrical shape, the intervening radius portion forms a xe2x80x9chumpxe2x80x9d which extends radially away from the hole forming mandrel.
In applications where gaskets are employed in openings of cast members having curved walls, such as manhole bases or the like, the gasket is held in place by two-piece mandrel assemblies such as the type described in co-pending application Ser. No. 09/533,424 filed Mar. 22, 2000 and specifically shown in FIG. 1 thereof. The embedment portion of the gasket is held between the inner and outer mandrel members, which are then secured to one another to hold the gasket in place. The mandrel assembly, with the gasket fixed in place, is then secured between inner core and outerjacket mold members employed to form the cast member, i.e. manhole base. In instances where the size of the opening requires that the gasket have a curvature in the horizontal plane, to generally conform to the curvature of the cored wall (or performed opening), the two-piece mandrel assembly is provided with a curved shape to impart some curvature to the embedment portion of the gasket.
After casting of the cast member (which may typically be a manhole base), the configuration of the gasket in the assembled position provides a large tolerance for the annular space between the inside opening of the entry hole and the outside diameter of the pipe. The radius portion, having a substantially U-shaped cross-section, provides a wide tolerance for annular deflection of the pipe as well as substantial offset placement of the pipe away from both the vertical and horizontal positions, the diameter of which is capable of being adjusted in addition to and independently of gasket thickness. The xe2x80x9crollingxe2x80x9d nature of the gasket when in the fully installed position enables the pipe and gasket to change their alignment due to settlement of the ground surrounding the cast member and pipe while assuring and retaining a rugged, liquid-tight seal.
It is therefore one object of the present invention to provide a novel method and apparatus for producing gaskets and for casting gaskets within an opening in cast members, the gasket being designed to receive a corrugated pipe which is easily pushed into the gasket without exertion by providing a inner diameter of the pipe engaging portion which is larger than the outer diameter of the pipe and utilizing clamping means to clamp the pipe engaging portion to an annular projection and/or annular recess to provide an excellent liquid-tight seal therebetween.